The patch below does not apply to the 4.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.
thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 47aee4d8e314384807e98b67ade07f6da476aa75 Mon Sep 17 00:00:00 2001 From: Minchan Kim <[email protected]> Date: Thu, 22 Oct 2015 13:32:19 -0700 Subject: [PATCH] thp: use is_zero_pfn() only after pte_present() check Use is_zero_pfn() on pteval only after pte_present() check on pteval (It might be better idea to introduce is_zero_pte() which checks pte_present() first). Otherwise when working on a swap or migration entry and if pte_pfn's result is equal to zero_pfn by chance, we lose user's data in __collapse_huge_page_copy(). So if you're unlucky, the application segfaults and finally you could see below message on exit: BUG: Bad rss-counter state mm:ffff88007f099300 idx:2 val:3 Fixes: ca0984caa823 ("mm: incorporate zero pages into transparent huge pages") Signed-off-by: Minchan Kim <[email protected]> Reviewed-by: Andrea Arcangeli <[email protected]> Acked-by: Kirill A. Shutemov <[email protected]> Cc: Mel Gorman <[email protected]> Acked-by: Vlastimil Babka <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: Rik van Riel <[email protected]> Cc: <[email protected]> [4.1+] Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 4b06b8db9df2..bbac913f96bc 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2206,7 +2206,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++, address += PAGE_SIZE) { pte_t pteval = *_pte; - if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { + if (pte_none(pteval) || (pte_present(pteval) && + is_zero_pfn(pte_pfn(pteval)))) { if (!userfaultfd_armed(vma) && ++none_or_zero <= khugepaged_max_ptes_none) continue; -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
